FindProtobuf3: allows (manual) selection between default version and eos-protobuf3 version

cmake/FindProtobuf3.cmake

@@ -15,20 +15,23 @@
 # (To distribute this file outside of CMake, substitute the full
 #  License text for the above reference.)
 
-set(PROTOBUF3_RPATH /usr/lib64/protobuf3)
+set(PROTOBUF3_ROOT=/usr)
+#set(PROTOBUF3_ROOT=/opt/eos)
+
+set(PROTOBUF3_RPATH ${PROTOBUF3_ROOT}/lib64/protobuf3)
 message(STATUS "PROTOBUF3_RPATH=${PROTOBUF3_RPATH}")
 
 set(PROTOBUF3_INCLUDE_PATH ${CMAKE_CURRENT_SOURCE_DIR})
 
 find_program(PROTOBUF3_PROTOC3_EXECUTABLE
-    NAMES protoc3
+    NAMES ${PROTOBUF3_ROOT}/bin/protoc3
     DOC "Version 3 of The Google Protocol Buffers Compiler"
 )
 message(STATUS "protoc3 is at ${PROTOBUF3_PROTOC3_EXECUTABLE} ")
 
 find_path(PROTOBUF3_INCLUDE_DIRS
   google/protobuf/message.h
-  PATHS /usr/include/protobuf3
+  PATHS ${PROTOBUF3_ROOT}/include/protobuf3
   NO_DEFAULT_PATH)
 message(STATUS "PROTOBUF3_INCLUDE_DIRS=${PROTOBUF3_INCLUDE_DIRS}")